How the kernel relies on its extensions to make your Mac work, and has highest privilege for stability and security. How this must change for Apple Silicon.
XNU
Adds details of the sequence of screens displayed at each stage, to help diagnose boot problems.
Single-diagram summary of how a modern Mac starts up in macOS 10.12 or 10.13, from pressing the Power button to running the kernel.
How macOS gets to load a hefty kernel and over 300 extensions so quickly: it cheats with a pre-linked kernelcache. And why you don’t see extensions loading in the log.
The Eclectic Light Company 